The present invention relates to supersonic airplanes, particularly to a supersonic airplane having a wing swingable from a conventional position orthogonal to the fuselage for subsonic flight and an oblique position relative to the fuselage for supersonic flight, and more particularly to the wing pivot location and wing pivot structure for such an airplane.
Certain aerodynamic characteristics of an oblique wing transonic airplane are discussed in two articles: "Transonic Transport Wings -- Oblique or Swept?", Jones, R. T. and Nisbet, J. W., Astronautics and Aeronautics, January, 1974, pages 40-47; and, "Aeroelastic Stability and Control of an Oblique Wing," Jones, R. T. and Nisbet, J.W., Aeronautical Journal, August, 1976, pages 365-369, both of which are expressly incorporated herein by reference. A phenomenon discussed in the aforementioned articles relates to the aeroelastic effect produced by an oblique wing airplane at supersonic flight speeds. Simply, the aeroelastic effect tends to cause the leading tip of an oblique wing to distort or bend upwardly, thereby increasing the angle of attack of that wing relative to the fuselage orientation. The aeroelastic effect on the oblique wing, which increases with increasing dynamic pressure, will induce both a pitch and a roll moment on the airplane. The pitch moment will tend to cause the nose of the fuselage to raise while the roll moment will cause the airplane to roll in the direction of the trailing tip of the oblique wing. One suggestion noted in the articles for counteracting the roll moment induced by the aeroelastic effect is to trim the airplane for level flight using control surfaces such as ailerons on the wing to counteract both the pitch and roll moments. However, trimming with the ailerons decreases the lift to drag ratio, and thus detracts from one of the primary advantages of the oblique wing over other transonic and supersonic airplane wing designs (such as swept wings, variable sweep wings and delta wings), namely a high lift to drag ratio.
Another aerodynamic phenomenon that occurs when an airplane is flown at supersonic speeds is that the center of pressure on the wing shifts aft from its location at subsonic flight speeds. The shift in the center of pressure will induce a downward pitch moment on the airplane. This downward pitch moment is usually counteracted by a combination of aircraft design techniques and by properly trimming the aircraft with pitch control surfaces, the latter of which, again, causes an undesirable reduction of the lift to drag ratio of the airplane.
It is a broad object of the present invention to provide an improvement in an oblique wing airplane to counteract the induced roll and pitch caused by the aeroelastic effect and the center of pressure shift just discussed. It is an additional object of the present invention to provide an improved and novel structure for interconnecting the wing and fuselage of an oblique wing airplane. Further objects of the present invention are to provide such an improved structure that is of relatively simple construction, and that will not affect adversely flight characteristics when the oblique wing is swung to a conventional configuration.